This disclosure generally relates to functionalized zeolite compositions and their use as catalysts for the production of bisphenols. The disclosure further relates to methods for preparing these functionalized zeolite compositions.
Bisphenols are valuable raw materials for producing polycarbonates. Polycarbonates are widely used in a variety of applications by virtue of their excellent physical properties, such as impact resistance, mechanical characteristics, transparency, and the like. Bisphenols are generally obtained by the reaction of a carbonyl compound, e.g., acetone, with a phenol in the presence of an acidic catalyst, such as mineral acids or acidic ion exchange resins. Due to environmental concerns from use of corrosive mineral acids, solid acid catalysts such as ion exchange resins have been increasingly used for preparing bisphenols. Furthermore, solid acid catalysts lead to a more efficient and simple separation of product stream and catalyst. Other types of solid acid catalysts, such as for example, synthetic alumino silicates, e.g., H-ZSM-5, H-Mordenite, and H-Y zeolite, as well as heteropolyacids have also been used for preparing bisphenols. However, all of these types of catalysts exhibit relatively low selectivities and/or reactivity.
One example of acidic ion exchange resins are the series of sulfonated polystyrene resins cross-linked with divinylbenzene, (PS-DVB). Frequently, a co-catalyst is used in conjunction with the acidic ion exchange resin catalyst, to improve the selectivity for bisphenol, and in particular, the para, para-bisphenol isomer. Co-catalysts can be present as unattached molecules in the bulk reaction matrix, e.g., “bulk co-catalysts”, or can be attached to the acidic ion exchange resin catalyst through ionic or covalent linkages. Mercaptans are a useful class of co-catalysts. More specifically, thiols, e.g., organosulfur compounds which are derivatives of hydrogen sulfide, can be used as co-catalysts. Numerous efforts have been made to improve the selectivity for bisphenols by varying the ratio of the mercaptan co-catalyst to the acidic catalyst. One approach that has recently been attempted is to use a acidic ion exchange resin catalyst having an attached co-catalyst, which are prepared, for example, by reacting a portion of the acidic groups of the acidic ion exchange resins with aminomercaptans, thereby resulting in catalysts containing both mercaptan and sulfonic acid groups.
When ion exchange resin catalysts are used for making bisphenols by reaction of phenols with carbonyl compounds, the lifetime of the catalyst is affected by factors, such as its mechanical strength and its tendency to foul. Furthermore, use of these catalysts requires pre-conditioning of the catalyst with phenol, especially in continuous processes. Pre-conditioning is generally done by passing the phenol through a packed bed of the ion exchange resin catalyst.
Thus, there remains a need for alternative catalysts that can be used for producing bisphenols with high selectivity while minimizing the formation of deleterious by-products. It would also be beneficial to have a catalyst with a solid acid matrix that is rigid and does not swell in the reaction medium to an undefined/non specific pore structure. Furthermore, there is a need for such catalysts which not only have built-in functionalities for performing as a catalyst and a co-catalyst, but which also afford improved bisphenol selectivity, particularly for the para, para-isomer. Moreover, there is also a need for such alternative catalysts that have potentially superior mechanical properties as compared to the traditionally used ion-exchange resins, thereby leading to improved catalyst lifetime and bisphenol productivity.